Sheath and Core Yarn for Thermoplastic Composite

ABSTRACT

A yarn containing a core of continuous filaments of an inorganic material and a sheath of staple fibers of a thermoplastic polymer is provided. The yarn can be formed into a fabric or unidirectional tape, which can then be heated under pressure to form a composite material that has excellent mechanical strength yet is lightweight. The fabric can be molded into a composite material having a two-dimensional or three-dimensional shape because of its excellent drapability. The composite material can be used in aircraft parts, automotive parts, marine parts, consumer electronic parts, and other products.

RELATED APPLICATION

The present application claims priority to U.S. Provisional ApplicationSer. No. 61/932,281, filed on Jan. 28, 2014, which is incorporatedherein in its entirety by reference thereto.

BACKGROUND OF THE INVENTION

Composite materials are materials made from two or more constituentmaterials, with different physical or chemical properties, that whencombined, produce a material with characteristics different from theindividual components. Combining the two or more constituent materialscan result in a composite material that is stronger, lighter, or lessexpensive when compared to traditional materials. Such compositematerials can be used to form aircraft parts, automotive parts, marineparts, consumer electronic parts, and other products where a lightweightyet strong material is desired.

Composite materials can be formed from the combination of athermoplastic material and an inorganic material, such as fiberglass, byseveral different methods, such as by alternating layers of a fiberglassyarn fabric and a thermoplastic yarn fabric, weaving separate yarns offiberglass and thermoplastic together in a fabric, by commingling afiberglass yarn and a thermoplastic yarn to form a single yarn, or bydipping a fiberglass fabric in a solvent a containing a thermoplasticpolymer. However, such methods, such as commingling, often result inpoor flow and fiber wet out, which results in a composite that hasexcessive voids. This can lead to difficulty in filling air voids whenthe composite is formed, resulting in a weakened composite, as fiberwetout is important for obtaining good load transfer from thethermoplastic resin to the reinforcing fiberglass. Further, the use ofsolvents can lead to environmental and health concerns. As such, a needexists for a composite that exhibits improved properties compared tocurrently available composites and that can be formed with better flowand fiber wet out. A need also exists for a method for forming acomposite that does not utilize a solvent based application system toalleviate environmental and health concerns.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present invention, a spun yarnis described that includes a core and a sheath. The core comprises fromabout 50 wt. % to about 90 wt. % of the spun yarn based on the totalweight of the spun yarn, and the sheath comprises from about 10 wt. % toabout 50 wt. % of the spun yarn based on the total weight of the spunyarn. In addition, the core includes continuous filaments of aninorganic material and the sheath includes staple fibers of athermoplastic polymer.

In one embodiment, the inorganic material can include fiberglass,carbon, ceramic, quartz, or a combination thereof. In an additionalembodiment, the thermoplastic polymer can include polyetherimide,polycarbonate, polypropylene, polyethylene, polyphenylene sulfide,polyethylene terephthalate, polybutylene terephthalate,polyethersulfone, polyetherketoneketone, polyetheretherketone,polyamide, or a combination thereof.

In still another embodiment, the staple fibers can have a length rangingfrom about 10 millimeters to about 75 millimeters. Meanwhile, thecontinuous filaments can be coated with a binder. Further, regardless ofthe materials used to form the spun yarn, the yarn can be corespun, ringspun, air jet spun, friction spun, or vortex spun. In one moreembodiment, the yarn can be formed into a fabric or unidirectional tape.The fabric can be a knitted, woven, or braided fabric.

In yet another embodiment, the present disclosure is directed to amethod for forming a spun yarn. The method includes introducing a coreof continuous filaments into a yarn spinning apparatus, where thecontinuous filaments include an inorganic material; and introducingstaple fibers into the yarn spinning apparatus, where the staple fibersinclude a thermoplastic polymer; and forming a sheath around the core ofcontinuous filaments. The yarn spinning apparatus causes the staplefibers to wrap around the core of continuous filaments to form thesheath. Further, the core constitutes from about 50 wt. % to about 90wt. % of the spun yarn and the sheath constitutes from about 10 wt. % toabout 50 wt. % of the spun yarn based on the total weight of the spunyarn.

In one particular embodiment, the method further includes coating thecontinuous filaments with a binder before introducing the staple fibers.

In an additional embodiment, the inorganic material used in the methodincludes fiberglass, carbon, ceramic, quartz, or a combination thereof.Further, the staple fibers used in the method include polyetherimide,polycarbonate, polypropylene, polyethylene, polyphenylene sulfide,polyethylene terephthalate, polybutylene terephthalate,polyethersulfone, polyetherketoneketone, polyetheretherketone,polyamide, or a combination thereof.

In still another embodiment, the method contemplates a spun yarn that iscorespun, ringspun, air jet spun, friction spun, or vortex spun.

In one more embodiment contemplated by the present disclosure, acomposite material that includes a fabric that further includes a spunyarn is contemplated. The spun yarn includes a core of continuousfilaments of an inorganic material and a sheath, of staple fibers of athermoplastic polymer. The composite material is formed by theapplication of heat and pressure to the fabric.

In one particular embodiment, the inorganic material can includefiberglass, carbon, ceramic, quartz, or a combination thereof. In stillanother embodiment, the staple fibers can include polyetherimide,polycarbonate, polypropylene, polyethylene, polyphenylene sulfide,polyethylene terephthalate, polybutylene terephthalate,polyethersulfone, polyetherketoneketone, polyetheretherketone,polyamide, or a combination thereof.

In yet another embodiment, the core can constitute from about 50 wt. %to about 90 wt. % of the spun yarn based on the total weight of the spunyarn. Meanwhile, the sheath can constitute from about 10 wt. % to about50 wt. % of the spun yarn based on the total weight of the spun yarn.Further, the staple fibers can have a length of from about 5 millimetersto about 75 millimeters. In addition, the yarn can be core spun, ringspun, air jet spun, friction spun, or vortex spun.

In still another embodiment of the present disclosure, a method forforming a composite material is disclosed. The method includes applyingheat and pressure to a fabric to form a composite material, where thefabric comprises a yarn, where the yarn includes a core of continuousfilaments of an inorganic material and a sheath of staple fibers of athermoplastic polymer, where the heat applied has a temperature greaterthan the melting point of the thermoplastic polymer, and where thepressure applied ranges from about 50 psi to about 2000 psi.

In one particular embodiment, the yarn can be core spun, ring spun, airjet spun, friction spun, or vortex spun.

In still another embodiment, the continuous filaments can be coated witha binder. In yet another embodiment, the composite material can beshaped into a molded article by placing the fabric into a mold beforeapplying heat and pressure.

In one more embodiment, the inorganic material can include fiberglass,carbon, ceramic, quartz, or a combination thereof. Meanwhile, the staplefibers can include polyetherimide, polycarbonate, polypropylene,polyethylene, polyphenylene sulfide, polyethylene terephthalate,polybutylene terephthalate, polyethersulfone, polyetherketoneketone,polyetheretherketone, polyamide, or a combination thereof. In oneparticular embodiment, the staple fibers can include polyetherimide andthe heat applied can have a temperature ranging from about 200° C. toabout 400° C. In still another embodiment, the staple fibers can includepolycarbonate and the heat applied can have a temperature ranging fromabout 100° C. to about 275° C.

Other features and aspects of the present invention are discussed ingreater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth more particularly in the remainder of the specification, includingreference to the appended figures, in which:

FIG. 1 is a schematic view of a standard commercially available air jetspinning machine for use in performing steps of preferred embodiments ofthe present method; and

FIG. 2 is a view in side elevation, partially cut away, of the yarnproduced by the machine of FIG. 1;

FIG. 3 shows a process for forming a two dimensional composite materialas contemplated by the present disclosure; and

FIG. 4 shows a process for forming a three-dimensional compositematerial as contemplated by the present disclosure.

DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS

Reference now will be made in detail to various embodiments of theinvention, one or more examples of which are set forth below. Eachexample is provided by way of explanation of the invention, notlimitation of the invention. In fact, it will be apparent to thoseskilled in the art that various modifications and variations may be madein the present invention without departing from the scope or spirit ofthe invention. For instance, features illustrated or described as partof one embodiment, may be used on another embodiment to yield a stillfurther embodiment. For the purposes of this application, like featureswill be represented by like numbers between the figures.

Generally speaking, the present disclosure is directed to a yarn, afabric, and composite material that can be utilized in applicationswhere a lightweight yet strong material is desired. By selectivelycontrolling the materials utilized in the core and sheath components ofthe yarn, as well as the size and weight percentage of the core andsheath components, a composite having improved properties due to betterflow and wetout is provided. For instance, the core is formed ofcontinuous filaments of an inorganic material, while the sheath isformed of staple fibers of a thermoplastic material. Without intendingto be limited by any particular theory, it is believed that the improvedproperties are due in part to the ability of the thermoplastic staplefibers of the sheath to be placed in very close proximity to the corecontinuous filaments. Further, once heated to form a composite, the corecan remain intact as a woven grid structure to provide properties neededin the composite application, while the thermoplastic sheath is meltedaround the core. The fabric of the present disclosure also has excellentdrapability so that, when forming a composite, the composite can beeasily molded into a curved, three-dimensional shape, such as aircraft,marine, automotive, or electronic components. As a load is applied tothe composite, the load is transferred from the melted thermoplasticstaple fibers to the reinforcing core of inorganic continuous filaments.

Core

The core of the yarn contemplated by the present disclosure can includeany suitable inorganic material. For instance, the core can includefiberglass, carbon, ceramic, quartz, or a combination thereof.Fiberglass composite is a fiber reinforced polymer made of a plasticmatrix reinforced by fine fibers of glass. It is also known as GFK orFRS and is a lightweight, extremely strong, and robust material. Theplastic matrix can be an epoxy, a thermosetting plastic (e.g., polyesteror vinylester) or a thermoplastic. Meanwhile, carbon fibers areextremely strong, thin fibers made by pyrolyzing synthetic fibers, suchas rayon, until charred. Ceramic fibers include small-dimensionfilaments or threads composed of a ceramic material, such as alumina orsilica. However, in some embodiments, it is also to be understood thatan organic material such as cellulose can be used in the core of theyarn.

The core can be in the form of one or more continuous filaments of theinorganic material, such as from about 1 to about 2000 filaments, suchas from about 25 to about 1850 filaments, such as from about 50 to about1700 filaments. The one or more filaments can each have a diameterranging from about 1 micron to about 50 microns, such as from about 2microns to about 40 microns, such as from about 3 microns to about 50microns. Regardless of the specific number and type of continuousfilaments utilized, the core of continuous filaments can be present inan amount ranging from about 50 wt. % to about 90 wt. %, such as fromabout 55 wt. % to about 85 wt. %, such as from about 60 wt. % to about80 wt. % based on the total weight of the yarn.

In some embodiments, the core of the yarn can be coated with a binderprior to further processing to incorporate the sheath staple fibers intothe yarn. The addition of the binder can enhance the attachment of thesheath staple fibers to the continuous filaments of the core of theyarn. The binder should be capable of withstanding temperatures of up toabout 400° C. without degrading, as forming a composite from the fabricand yarn of the present disclosure may require heating the fabric tosuch a temperature. If the binder begins to degrade during forming ofthe composite, dark streaks would be formed in the composite, whichresults in an appearance that is not aesthetically pleasing. The bindercan be applied to the core of continuous filament(s) in an amountranging from about 0.1 wt. % to about 5 wt. %, such as from about 0.2wt. % to about 2.5 wt. %, such as from about 0.25 wt. % to about 1 wt. %based on the total weight of the yarn.

Sheath

The sheath can include staple fibers formed from a thermoplasticmaterial, such as polyetherimide, polycarbonate, polypropylene,polyethylene, polyphenylene sulfide, polyethylene terephthalate,polybutylene terephthalate, polyethersulfone, polyetherketoneketone,polyetheretherketone, polyamide, or a combination thereof.

In some embodiments, the thermoplastic can be renewable or bio-based.For instance, polyamide 11, which is derived from vegetable oil, andbiopolypropylene, which is derived from sugarcane, can be used assuitable thermoplastics in the yarn and composite materials of thepresent invention.

In one particular embodiment, the thermoplastic staple fiber can be apolyetherimide. The polyetherimide fiber can include structural units I:

wherein T is a divalent bridging group, selected from the groupconsisting of a bond, O, S, SO, CO, SO₂, a C₁-C₂₀ aliphatic radical, aC₂-C₂₀ cycloaliphatic radical, and a C₂-C₂₀ aromatic radical; and R1 isdivalent radical selected from a C₁-C₂₀ aliphatic radical, a C₂-C₂₀cycloaliphatic radical, or a C₂-C₂₀ aromatic radical. Typically, thedivalent bridging group T may be attached to the aromatic rings ofstructural unit I at positions such as the 3,3′; 4,4′; 3,4′; or 4,3′.

In one embodiment, the divalent bridging group T can be a —O—Z—O—wherein Z is a C₁-C₂₀ aliphatic radical, a C₂-C₂₀ cycloaliphaticradical, or a C₂-C₂₀ aromatic radical. In another embodiment, Zcomprises structural units II

wherein Q includes but is not limited to a divalent moiety selected fromthe group consisting of is a C₁-C₁₂ aliphatic radical, a C₃-C₁₂cycloaliphatic radical, a C₄-C₁₈ aromatic radical, —O—, —S—, —C(O)—,—SO₂—, —SO—, —C_(y)H_(2y)— (y being an integer from 1 to 8), andfluorinated derivatives thereof, for example perfluoroalkylene groups.Illustrative examples of the C_(y)H_(2y) group include but are notlimited to methylene, ethylene, ethylidene, propylene, andisopropylidene.

In some embodiments, the polyetherimide may be a copolymer. Mixtures ofpolyetherimides may also be employed. The polyetherimide can be preparedby any of the methods well known to those skilled in the art, includingthe reaction of an aromatic bis(ether anhydride) with an organicdiamine. The polyetherimide fiber comprises structural units derivedfrom a diamine and a bis(ether anhydride).

Examples of specific aromatic bis anhydrides and organic diamines aredisclosed, for example, in U.S. Pat. Nos. 3,972,902 and 4,455,410 andU.S. Patent Application Publication No. 2010/0048853, which areincorporated herein by reference. Non-limiting examples of suitablebis(ether anhydrides) include:2,2-bis(4-(3,4-dicarboxyphenoxy)phenyl)propane dianhydride;4,4′-bis(3,4-dicarboxyphenoxy)diphenyl ether dianhydride. Illustrativeexamples of aromatic bis anhydrides include hydride;4,4′-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride;4,4′-bis(3,4-dicarboxyphenoxy)benzophenone dianhydride;4,4′-bis(3,4-dicarboxyphenoxy)diphenyl sulfone dianhydride;2,2-bis([4-(2,3-dicarboxyphenoxy)phenyl]propane dianhydride;4,4′-bis(2,3-dicarboxyphenoxy)diphenyl ether dianhydride;4,4′-bis(2,3-dicarboxyphenoxy)diphenyl sulfide dianhydride;4,4′-bis(2,3-dicarboxyphenoxy)benzophenone dianhydride;4,4′-bis(2,3-dicarboxyphenoxy)diphenyl sulfone dianhydride;4-(2,3-dicarboxyphenoxy)-4′-3,4-dicarboxyphenoxy)diphenyl-2,2-propanedianhydride; 4-(2,3-dicarboxyphenoxy)4′-(3,4-dicarboxyphenoxy)diphenylether dianhydride;4-(2,3-dicarboxyphenoxy)4′-(3,4-dicarboxyphenoxy)diphenyl sulfidedianhydride;4-(2,3-dicarboxyphenoxy)-4′-(3,4-dicarboxyphenoxy)benzophenonedianhydride; 4-(2,3-dicarboxyphenoxy)-4′-(3,4-dicarboxyphenoxy)diphenylsulfone dianhydride; and combinations thereof.

In general, any diamine compound may be employed for the synthesis ofthe polyetherimide fiber. Non-limiting examples of organic diaminesinclude ethylenediamine, propylenediamine, trimethylenediamine,diethylenetriamine, triethylene tetramine, hexamethylenediamine,heptamethylenediamine, octamethylenediamine, nonamethylenediamine,decamethylenediamine, 1,12-dodecanediamine, 1,18-octadecanediamine,3-methylheptamethylenediamine, 4,4-dimethylheptamethylenediamine,4-methylnonamethylenediamine, 5-methylnonamethylenediamine,2,5-dimethylhexamethylenediamine, 2,5-dimethylheptamethylenediamine,2,2-dimethylpropylenediamine, N-methyl-bis(3-aminopropyl)amine,3-methoxyhexamethylenediamine, 1,2-bis(3-aminopropoxy)ethane,bis(3-aminopropyl)sulfide, 1,4-cyclohexanediamine,bis-(4-aminocyclohexyl)methane, m-phenylenediamine, p-phenylenediamine,2,4-diaminotoluene, 2,6-diaminotoluene, m-xylylenediamine,p-xylylenediamine, 2-methyl-4,6-diethyl-1,3-phenylene-diamine,5-methyl-4,6-diethyl-1,3-phenylene-diamine, benzidine,3,3′-dimethylbenzidine, 3,3′-dimethoxybenzidine, 1,5-diaminonaphthalene,bis(4-aminophenyl)methane,bis(2-chloro-4-amino-3,5-diethylphenyl)methane,bis(4-aminophenyl)propane, 2,4-bis(p-amino-t-butyl)toluene,bis(p-amino-t-butylphenyl)ether, bis(p-methyl-o-aminophenyl)benzene,bis(p-methyl-o-aminopentyl)benzene, 1,3-diamino-4-isopropylbenzene,bis(4-aminophenyl)sulfide, bis-(4-aminophenyl)sulfone, andbis(4-aminophenyl)ether. Mixtures of these compounds may also be used.In some embodiments the organic diamine comprises m-phenylenediamine,p-phenylenediamine, sulfonyl dianiline, or a combination comprising oneor more of the foregoing.

Representative polyetherimides may include those described in U.S. Pat.Nos. 3,847,867; 4,650,850; 4,794,157; 4,855,391; 4,820,781; and,4,816,527; as well as U.S. Patent Application Publication No.2012/0107551, which are incorporated herein by reference.

The polyetherimide resin can have a weight average molecular weight (Mw)of about 500 to about 1,000,000 grams per mole (g/mole), in anotherembodiment a Mw of about 5,000 g/mole to about 500,000 g/mole, and yetin another embodiment from about 10,000 g/mole to about 75,000 g/mole asmeasured by gel permeation chromatography, using a polystyrene standard.

In another particular embodiment, the thermoplastic staple fiber can bea polycarbonate. More specifically, the polycarbonate can be an aromaticpolycarbonate. The aromatic polycarbonate employed, according to anembodiment, can be prepared by reacting a dihydric phenol with acarbonate precursor. The dihydric phenol which may be employed toprovide such aromatic carbonate polymers are mononuclear or polynucleararomatic compounds, containing as functional groups two hydroxyradicals, each of which is attached directly to a carbon atom of anaromatic nucleus. Typical dihydric phenols are: 2,2-bis(4-hydroxyphenyl)propane; hydroquinone; resorcinol; 2,2-bis(4-hydroxyphenyl) pentane;2,4′-(dihydroxydiphenyl) methane; bis(2 hydroxyphenyl) methane;bis(4-hydroxyphenyl) methane;1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane; fluorenonebisphenol, 1,1-bis(4-hydroxyphenyl)ethane; 3,3-bis(4-hydroxyphenyl)pentane; 2,2-dihydroxydiphenyl; 2,6-dihydroxynaphthalene;bis(4-hydroxydiphenyl)sulfone; bis(3,5-diethyl-4-hydroxyphenyl)sulfone;2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane; 2,4′-dihydroxydiphenylsulfone; 5′-chloro-2,4′-dihydroxydiphenyl sulfone;bis-(4-hydroxyphenyl)diphenyl sulfone; 4,4′-dihydroxydiphenyl ether;4,4′-dihydroxy-3,3′-dichlorodiphenyl ether; 4,4-dihydroxy-2,5-diphenylether; and the like. Other dihydric phenols used in the preparation ofthe above polycarbonates are disclosed in U.S. Pat. Nos. 2,999,835;3,038,365; 3,334,154; and 4,131,575, which are incorporated herein byreference.

Aromatic polycarbonates can be manufactured by known processes, such as,for example and as mentioned above, by reacting a dihydric phenol with acarbonate precursor, such as phosgene, in accordance with the methodsset forth in, for example, U.S. Pat. No. 4,123,436, or bytransesterification processes such as are disclosed in U.S. Pat. No.3,153,008, both of which are incorporated herein by reference, as wellas other processes known to those skilled in the art.

As noted above, it is also possible to employ two or more differentdihydric phenols or a copolymer of a dihydric phenol with a glycol orwith a hydroxy- or acid-terminated polyester or with a dibasic acid inthe event a carbonate copolymer or interpolymer rather than ahomopolymer is desired for use in the preparation of the polycarbonatemixtures. Branched polycarbonates are also useful, such as are describedin U.S. Pat. No. 4,001,184, which is incorporated herein by reference.Also, there can be utilized blends of linear polycarbonate and abranched polycarbonate. Moreover, blends of any of the above materialsmay be employed to provide the aromatic polycarbonate. One aromaticcarbonate is a homopolymer, e.g., a homopolymer derived from2,2-bis(4-hydroxyphenyl)propane (bisphenol-A) and phosgene.

The staple fibers can have a staple length ranging from about 5millimeters to about 75 millimeters, such as from about 10 millimetersto about 65 millimeters, such as from about 20 millimeters to about 55millimeters. Further, the staple fibers can have a linear mass densityranging from about 0.25 denier to about 20 denier, such as from about0.5 denier to about 15 denier, such as from about 0.75 denier to about10 denier.

Regardless of the specific number and type of staple fibers utilized,the sheath of staple fibers can be present in an amount ranging fromabout 10 wt. % to about 50 wt. %, such as from about 15 wt. % to about45 wt. %, such as from about 20 wt. % to about 40 wt. % based on thetotal weight of the yarn.

Types of Yarn Spinning

Referring now to the drawings, and in particular to FIGS. 1 and 2, inone embodiment, a form of an intermediate yarn 100 for use in variousembodiments of the present disclosure is produced on a standard MurataJet Spinning (MJS) or Murata Vortex Spinning (MVS) spinning frame 300.The spinning frame 300, as is well known in the art, includes a staplefiber 500 supply which feeds the staple fibers 500 through a trumpet700, into a drafting zone. The staple fibers can be processed by acarding machine into a solid controllable and soft form. The draftingzone comprises a pair of back rolls 900, a pair of middle rolls 110, apair of apron rolls 130, and a pair of front rolls 150. If desired, aguide or condenser may be included between the middle rolls 110 andapron rolls 130.

As shown in FIG. 1, the spinning frame 300 is set up with a standardcore attachment for inclusion of a core. A continuous filament core yarn170 is fed through a guide 190 into the spinning frame at the forwardend of the drafting zone, at front rolls 150.

The front rolls 150 feed the continuous filament yarn 170 and draftedstaple fibers into a spinning zone comprising spinning nozzles 210 anddelivery rolls 230 which form the staple fibers 500 into a spun sheathsurrounding and hiding the continuous filament core yarn 170 inaccordance with well-known principles.

The completed corespun yarn 100 is passed through a yarn clearer 250 androlled onto a core package 270.

The corespun yarn 1 which forms an intermediate yarn for use in thepresent invention is shown in FIG. 2. In such an embodiment, the staplefibers 500, and hence the spun sheath 500, of the yarn 100 are formed ofa thermoplastic polymer as discussed above. Meanwhile, the continuousfilament core can be formed of a multifilament bundle, such as amultifilament bundle of an inorganic material as discussed above. Such aprocess is described in U.S. Pat. No. 7,841,162, which is incorporatedherein by reference.

In addition to contemplating yarns formed by core spinning, air jetspinning, or vortex spinning as described above, the present disclosurealso contemplates yarns formed by ring spinning or friction spinning. Inparticular, ring spinning requires a separate winding process, which isused to consolidate the smaller ring spinning bobbins of the core spunyarn onto larger packages.

Ring spinning is a continuous process where a fiber bundle is firstattenuated by using drawing rollers, then spun and wound around arotating spindle which in its turn is contained within an independentlyrotating ring flyer. Ring spinning is generally described in U.S. Pat.No. 8,079,206, which is incorporated herein by reference.

Meanwhile, in friction spinning, individual fibers are transported byair currents and deposited in a spinning zone. The fibers assemblethrough a feed tube onto a core yarn core or filament(s) within theshear field, which is provided by two rotating spinning drums where theyarn core is disposed in between them. The shear causes the individualsheath fibers to wrap around the core yarn. Friction spinning isgenerally described in U.S. Pat. No. 4,107,909, which is incorporatedherein by reference.

Regardless of the method by which the yarn of the present disclosure isspun, the resulting yarn can have a yarn weight of from about 1 cottoncount (Ne) to about 20 Ne, such as from about 2.5 Ne to about 15 Ne,such as from about 5 Ne to about 10 Ne. The cotton count (Ne) refers tonumber of 840 yard lengths per pound of yarn.

Fabric Forming Process

Further, regardless of the manner by which the yarn of the presentdisclosure is spun, after spinning, the yarn can be formed into a fabricutilizing any suitable method known by one having ordinary skill in theart. For instance, the fabric can be woven, knitted, or braided. In oneparticular embodiment, the fabric can be in the form of a unidirectionaltape. When in the form of a woven fabric, the weave of the woven fabricelement may be a satin weave, such as a standard 8 harness satin weave,or any other suitable weave.

In an additional embodiment, prior to forming the yarn into a fabric,the yarn can be coated with a sizing. Sizing of the yarn helps to reducebreakage of the yarn. For instance, when a yarn is woven into a fabricusing a weaving machine, the yarns are subjected to several types ofactions (i.e., cyclic strain, flexing, abrasion) at various loom partsand inter yarn friction. By coating the sheath (e.g., staple fibers) ofthe yarn with a sizing, the abrasion resistance or strength of the yarnwill improve. Different types of water soluble polymers called textilesizing agents/chemicals such as modified starch, polyvinyl alcohol(PVA), carboxymethyl cellulose (CMC), acrylates can be used to protectthe yarn. Wax can also be added to reduce the abrasiveness of the yarn.In one particular embodiment of the present disclosure, the sizing agentcan include PVA, which is cold water soluble. Regardless of the sizingused, the sizing can be applied in an amount ranging from about 0.5 wt.% to about 20 wt. %, such as from about 2 wt. % to about 15 wt. %, suchas from about 5 wt. % to about 10 wt. % based on the total weight of theyarn. In some embodiments, to achieve the weight percent of sizingdescribed above, in a woven fabric, the warp yarns were treated with thesizing while the weft yarns were left untreated. For instance, in oneparticular embodiment, the warp yarns can be treated with 10 wt. % sizebased on the weight of the warp yarns, where the warp yarns make up 51wt. % of the fabric and the weft yarns make up 40 wt. % of the fabric,so that the wt. % of the sizing used based on the total weight of theyarns (warp and weft) was about 5.1 wt. %.

The sizing agent can optionally be removed by washing (desizing) afterforming the yarn into a fabric if the sizing agent is not compatiblewith the resin in order to reduce contamination that may be associatedwith the sizing agent. However, it is also to be understood thatdesizing is not required, such as when the sizing agent is compatiblewith the resin used. Desizing generally involves treating the fabricwith the desizing agent, allowing the desizing agent to degrade orsolubilize the size material, and finally washing the fabric to removethe degradation products. Any suitable desizing process can be used. Inparticular, when certain types of PVA are used as the sizing agent, thefabric can be desized by rinsing in cold water. The water replaces thesize on the outer surface of the yarn in the fabric, and absorbs withinthe yarn to displace any remaining size residue.

Regardless of the method by which the fabric of the present disclosureis formed, the resulting fabric can include from about 5 to about 80ends/inch, such as from about 10 to about 70 ends/inch, such as fromabout 15 to about 60 ends/inch. In one embodiment, the fabric caninclude 57 ends/inch. Further, the resulting fabric can include fromabout 5 to about 78 picks/inch, such as from about 10 to about 68picks/inch, such as from about 15 to about 58 picks/inch. In oneparticular embodiment, the fabric can include 54 picks/inch.

Further, the resulting fabric can have a basis weight ranging from about10 grams per square meter (gsm) to about 500 gsm, such as from about 20gsm to about 475 gsm, such as from about 30 gsm to about 450 gsm beforedesizing. Meanwhile, after desizing, the fabric can have a basis weightranging from about 9 gsm to about 495 gsm, such as from about 18 gsm toabout 465 gsm, such as from about 27 gsm to about 440 gsm. For instance,in one particular embodiment, a fabric having a basis weight of about417 gsm can be made, where 10 wt. % of sizing is added on to the warpyarns, which make up 51 wt. % of the fabric, resulting in a fabric,including sizing, having a basis weight of about 438 gsm.

Composite Forming Process

Once a fabric or unidirectional tape is formed from the spun yarn of thepresent disclosure, in some embodiments, the fabric or unidirectionaltape can be formed into a composite via the application of heat andpressure, although it is to be understood that the composite can also beformed via other methods, such as via vacuum forming, which generallyrequires that the fabric or unidirectional tape is preheated.

In one embodiment, the composite can be formed by placing the fabricbetween two flat portions of a mold, then applying heat and pressure toform a two-dimensional composite that is lightweight but has highstrength. As shown in FIG. 3, a method for forming a thermoplasticcomposite material 404, according to one embodiment of the presentdisclosure, includes the steps of placing a fabric 400 in a cavity 403formed by molds 401 and 402. The fabric 400 is then molded to form acomposite 404 by heating the fabric 400 such that the temperature of thefabric 400 becomes higher than the melting point of the thermoplasticstaple fibers that form the sheath of the yarn used to form the fabric400. Further, as shown in FIG. 4, because the fabric has gooddrapability, the fabric can be placed in a three-dimensional mold, andthe fabric can be formed into a shape having at least one fold 405 torender the composite material 404 three-dimensional after theapplication of heat and pressure. The fabric can be molded into acomposite having any suitable shape. For instance, the molded compositecan have one or more curves, bends, folds, or angles.

The temperature of the heat applied to the fabric to form the compositeis higher than the melting temperature of the thermoplastic staplefibers. For instance, when polyetherimide is used as the thermoplasticpolymer for the staple fibers, the heat applied can range from about200° C. to about 400° C., such as from about 225° C. to about 375° C.,such as from about 250° C. to about 350° C., depending on the particulargrade of polyetherimide utilized. Meanwhile, when polycarbonate is usedas the thermoplastic polymer for the staple fibers, the heat applied canrange from about 100° C. to about 275° C., such as from about 125° C. toabout 270° C., such as from about 150° C. to about 265° C.

Generally, internal pressures within the mold can range from about 50psi to about 2000 psi, such as from about 60 psi to about 1500 psi, suchas from about 70 psi to about 1250 psi. Further, the heat and pressurecan be applied for a time frame ranging from about 10 seconds to about180 minutes, such as from about 30 second to about 150 minutes, such asfrom about 1 minute to about 120 minutes, depending on the temperaturesand pressures applied, as well as the thermoplastic polymer utilized.

When formed as described above, the composite of the present inventioncan exhibit a tensile strength of from about 120 MegaPascals (MPa) toabout 500 MPa, such as from about 130 MPa to about 480 MPa, such as fromabout 140 MPa to about 460 MPa. Further, the composite of the presentinvention can exhibit a tensile modulus of from about 10 GigaPascals(GPa) to about 40 GPa, such as from about 12.5 GPa to about 35 GPa, suchas from about 15 GPa to about 30 GPa. Additionally, the composite of thepresent invention can exhibit a compression strength of from about 30MPa to about 600 MPa, such as from about 35 MPa to about 550 MPa, suchas from about 40 MPa to about 500 MPa. In addition, the composite of thepresent invention can exhibit a compression modulus of from about 5 GPato about 45 GPa, such as from about 7.5 GPa to about 40 GPa, such asfrom about 10 GPa to about 35 GPa. Further, the composite of the presentinvention can exhibit a shear strength of from about 30 MPa to about 100MPa, such as from about 40 MPa to about 90 MPa, such as from about 50MPa to about 80 MPa. Additionally, the composite of the presentinvention can exhibit a flexural strength of from about 120 MPa to about700 MPa, such as from about 130 MPa to about 675 MPa, such as from about140 MPa to about 650 MPa. In addition, the composite of the presentinvention can exhibit a flexural modulus of from about 10 GPa to about35 GPa, such as form about 15 GPa to about 30 GPa, such as from about 20GPa to about 25 GPa.

The present invention may be better understood with reference to thefollowing examples.

Example 1

In Example 1, samples 1-4 were tested for their tensile properties,in-plane shear properties, and flexural properties. As shown in Table 1,the warp tension properties (e.g., tensile strength and tensile modulus)were determined according to ASTM D3039 (“Standard Test Method forTensile Properties of Polymer Matrix Composite Materials”), the ±45°laminate tensile properties (e.g., shear strength) were determinedaccording to ASTM D3518 (“Standard Test Method for In-Plane ShearResponse of Polymer Matrix Composite Materials by Tensile Test of a ±45°Laminate”), and the warp flexural properties (e.g., flexural strengthand flexural modulus) were determined according to ASTM D790 (“StandardTest Methods for Flexural Properties of Unreinforced and ReinforcedPlastics and Electrical Insulating Materials”).

For samples 1-2, a spun yarn was formed that included a core offiberglass continuous filaments and a sheath of polyetherimide (PEI)staple fibers. The fiberglass filaments each had a diameter of 6microns, and the core included a bundle of 816 continuous filaments. ThePEI staple fibers had a linear mass density of 2 denier per filament anda length of 2 inches (50.8 millimeters). The spun yarn included 34 wt. %staple fibers and 66 wt. % continuous filaments. The core of continuousfilaments was coated with 0.3 wt. % of compatible binder. The core andsheath were spun into yarn on an MJS spinning system having a targetyarn weight of 5.9 Ne. Then, the yarn was woven into a fabric, where thewarp yarns only (51 wt. % of the total yarn) were treated with 10 wt. %of L1000 sizing, which was removed before consolidation. The fabric wasan 8 harness satin weave fabric having a basis weight of 434 gsm beforedesizing. The fabric was 53 inches wide and included 57 ends/inch and 54picks/inch.

For samples 3-4, a woven fiberglass fabric (type 7781, 8 harness satinweave) was coated with a polymer in powder form by dissolving thepolymer in solvent and then dipping the fabric in the resultingsolution. For sample 3, the polymer was PEI, while for sample 4, thepolymer was phenolic type thermoset resin. The polymer was present in anamount of 33 wt. % for samples 3-4. After forming each of the fabricsfor Samples 1-4 of Example 1, a consolidation step was carried out at aspecified temperature and pressure to form a composite material havingthe properties shown below in Table 1.

TABLE 1 ±45° Warp Tension Tension Warp Flex Polymer Temp PressureStrength Modulus Strength Strength Modulus Sample Polymer Wt. % (° C.)(psi) (MPa) (GPa) (MPa) (MPa) (GPa) 1 PEI staple fibers 34 330 435.1 — —68.9 467.5 24.1 2 PEI staple fibers 34 310 217.6 — — 71.7 340.6 22.7 3PEI powder 33 310 217.6 450.9 26.2 128.9 650.2 26.2 4 Thermoset 33 — —448.2 26.2 103.4 599.8 23.4 phenolic resin

As shown in samples 1-2, increasing the pressure when forming thecomposite material resulted in a higher flexural strength and modulus.Further, as shown, samples 1-2 have similar flexural moduli as comparedto samples 3-4, but without requiring the use of solvents to form thesamples.

Example 2

In Example 2, a spun yarn was formed that included a core of fiberglasscontinuous filaments and a sheath of polycarbonate staple fibers. Thefiberglass filaments each had a diameter of 6 microns, and the coreincluded a bundle of 816 continuous filaments. The polycarbonate staplefibers had a linear mass density of 2 denier per filament and a lengthof 2 inches (50.8 millimeters). The spun yarn included 33.4 wt. % staplefibers and 66.6 wt. % continuous filaments.

The core of continuous filaments was coated with 0.3 wt. % of compatiblebinder. The core and sheath were spun into yarn on an MJS spinningsystem having a target yarn weight of 5.9 Ne. Then, the yarn was woveninto a fabric, where the warp yarns only (51 wt. % of the total yarn)were treated with 10 wt. % of L1000 sizing. The fabric was an 8 harnesssatin weave fabric having a basis weight of 434 gsm before desizing. Thefabric was 53 inches wide and included 57 ends/inch and 54 picks/inch.After forming the fabric in Example 2, a consolidation step was carriedout to form a composite material.

Example 3

In Example 3, samples 1-10 were tested for their tensile properties,in-plane shear properties, and flexural properties. As shown in Table 2,the warp tension properties (e.g., tensile strength and tensile modulus)were determined according to ASTM D3039 (“Standard Test Method forTensile Properties of Polymer Matrix Composite Materials”), the warpcompression properties (e.g., compression strength and compressionmodulus) were determined according to ASTM D6641 (“Standard Test Methodfor Compressive Properties of Polymer Matrix Composite Materials Using aCombined Loading Compression (CLC) Test Fixture”), the ±45° laminatetensile properties (e.g., shear strength) were determined according toASTM D3518 (“Standard Test Method for In-Plane Shear Response of PolymerMatrix Composite Materials by Tensile Test of a ±45° Laminate”), and thewarp flexural properties (e.g., flexural strength and flexural modulus)were determined according to ASTM D790 (“Standard Test Methods forFlexural Properties of Unreinforced and Reinforced Plastics andElectrical Insulating Materials”).

For sample 1, a woven fiberglass fabric (type 7781, 8 harness satinweave) was coated with polyetherimide (PEI) in powder form by dissolvingthe polymer in solvent and then dipping the fabric in the resultingsolution. The fiberglass filaments in the fabric each had a diameter of6 microns, and the core included a bundle of 816 continuous filaments.The PEI was present in an amount of 33 wt. %, while the fiberglass waspresent in an amount of 67 wt. %.

For samples 2-6, a spun yarn was formed that included a core offiberglass continuous filaments and a sheath of polyetherimide (PEI)staple fibers. The fiberglass filaments each had a diameter of 6microns, and the core included a bundle of 816 continuous filaments. ThePEI staple fibers had a linear mass density of 2 denier per filament anda length of 2 inches (50.8 millimeters). The spun yarn included 34 wt. %staple fibers and 66 wt. % continuous filaments. The core of continuousfilaments was coated with 0.3 wt. % of compatible binder. The core andsheath were spun into yarn on an MJS spinning system having a targetyarn weight of 5.9 Ne. Then, the yarn was woven into a fabric, where thewarp yarns only (51 wt. % of the total yarn) were treated with 10 wt. %of L1000 sizing, which was removed before consolidation. The fabric wasan 8 harness satin weave fabric having a basis weight of 434 gsm beforedesizing. The fabric was 53 inches wide and included 57 ends/inch and 54picks/inch.

For sample 7, a woven fiberglass fabric (type 7581, 8 harness satinweave) was coated with polycarbonate in powder form by dissolving thepolymer in solvent and then dipping the fabric in the resultingsolution. The fiberglass filaments in the fabric each had a diameter of9 microns, and the core included a bundle of 408 continuous filaments.The polycarbonate was present in an amount of 34 wt. %, while thefiberglass was present in an amount of 66 wt. %.

For sample 8, a spun yarn was formed that included a core of fiberglasscontinuous filaments and a sheath of polycarbonate staple fibers. Thefiberglass filaments each had a diameter of 6 microns, and the coreincluded a bundle of 816 continuous filaments. The polycarbonate staplefibers had a linear mass density of 2 denier per filament and a lengthof 2 inches (50.8 millimeters). The spun yarn included 34 wt. % staplefibers and 66 wt. % continuous filaments. The core of continuousfilaments was coated with 0.3 wt. % of compatible binder. The core andsheath were spun into yarn on an MJS spinning system having a targetyarn weight of 5.9 Ne. Then, the yarn was woven into a fabric, where thewarp yarns only (51 wt. % of the total yarn) were treated with 10 wt. %of L1000 sizing, which was removed before consolidation. The fabric wasan 8 harness satin weave fabric having a basis weight of 434 gsm beforedesizing. The fabric was 53 inches wide and included 57 ends/inch and 54picks/inch.

For samples 9-10, a spun yarn was formed that included a core offiberglass continuous filaments and a sheath of polyethyleneterephthalate (PET) fibers. The fiberglass filaments each had a diameterof 7 microns, and the core included a bundle of 204 continuousfilaments. The PET yarn had a linear mass density of 1.2 denier perfilament and a length of 1.5 inches (38.1 millimeters). The spun yarnincluded 60 wt. % PET yarn and 40 wt. % continuous fiberglass filaments.The core of continuous filaments was coated with 1.5 wt. % ofnon-compatible binder. The core and sheath were spun into yarn on an MJSspinning system having a target yarn weight of 11 Ne. Then, the yarn waswoven into a fabric, where the warp yarns only (61 wt. % of the totalyarn) were treated with 6 wt. % of predominately PVOH sizing, which wasnot removed before consolidation. The fabric was a 2×1 twill and had abasis weight of 237 gsm before desizing. The fabric was 78 inches wideand included 66 ends/inch and 42 picks/inch.

For each of the samples 1-10 in Example 3, after forming each of thefabrics, a consolidation step was carried out for a specified period oftime and at a specified temperature and pressure to form a compositematerial having the properties shown below in Table 2.

TABLE 2 Warp Warp Warp Ply Tension Compression ±45° Flex Thick- Poly-Time Pres- Modu- Modu- Tension Modu- ness mer (min- Temp sure Strengthlus Strength lus Strength Strength lus Sample Polymer Layers (mm) Wt. %utes) (° C.) (psi) (MPa) (GPa) (MPa) (GPa) (MPa) (MPa) (GPa) 1 PEI — —33 20 325 290.1 450.9 26.2 723.9 29.0 128.9 650.2 26.2 powder 2 PEI 122.6 34 30 330 435.1 354.4 21.9 329.1 30.4 68.9 467.5 24.1 staple fibers3 PEI 12 2.7 34 30 310 217.6 342.1 19.8 201.9 27.2 71.7 340.6 22.7staple fibers 4 PEI 12 2.6 34 30 310 652.7 362.5 21.4 254.6 26.5 — 427.523.9 staple fibers 5 PEI 12 2.2 34 120  330 652.7 440.6 27.6 440.6 31.6— 634.3 30.3 staple fibers 6 PEI 12 2.6 34 30 330 435.1 372.3 23.7 423.326.1 — 530.9 23.4 staple fibers 7 Polycar- — 6.1 34 — — — 461.9 23.4448.2 26.1 — 730.8 26.2 bonate powder 8 Polycar- 12 — 34 30 260 290.1353 21.7 213.7 26.9 — 342.7 21.4 bonate staple fibers 9 Polyeth- 20 0.12 60 — — — — — 40.67 6.79 — — — ylene tere- phtahlate fibers 10Polyeth- 12  0.11 60 — — — 143.7 15.2 — — — 142.2 15.6 ylene tere-phtahlate fibers

As shown from a comparison of samples 2-6 in Example 3, increasing thetime, temperature, and pressure used to form the PEI thermoplasticcomposite material when forming the composite material generally resultsin a higher tensile strength and modulus, a higher compression strengthand modulus, and a higher flexural strength and modulus. Further, asshown, PEI staple fiber samples 2-6 have similar tensile, warp, andflexural moduli as compared to PEI powder sample 1, but withoutrequiring the use of solvents to form samples 2-6. In addition, as shownfrom a comparison of samples 7 and 8, polycarbonate staple fiber sample8 has similar tensile, warp, and flexural moduli as compared topolycarbonate powder sample 7, but without requiring the use of solventsto form sample 8. The ability to form fiberglass and PET thermoplasticcomposite materials was also demonstrated, as shown by samples 9 and 10.

While the invention has been described in detail with respect to thespecific embodiments thereof, it will be appreciated that those skilledin the art, upon attaining an understanding of the foregoing, mayreadily conceive of alterations to, variations of, and equivalents tothese embodiments. Accordingly, the scope of the present inventionshould be assessed as that of the appended claims and any equivalentthereto.

1-10. (canceled)
 11. A composite material comprising a fabric, thefabric comprising a spun yarn, the spun yarn comprising: a core, whereinthe core comprises continuous filaments of an inorganic material; and asheath, wherein the sheath comprises staple fibers of a thermoplasticpolymer, wherein the composite material is formed by the application ofheat and pressure to the fabric.
 12. The composite material of claim 11,wherein the inorganic material comprises fiberglass, carbon, ceramic,quartz, or a combination thereof, and wherein the staple fibers comprisepolyetherimide, polycarbonate, polypropylene, polyethylene,polyphenylene sulfide, polyethylene terephthalate, polybutyleneterephthalate, polyethersulfone, polyetherketoneketone,polyetheretherketone, polyamide, or a combination thereof.
 13. Thecomposite material of claim 11, wherein the core constitutes from about50 wt. % to about 90 wt. % of the spun yarn based on the total weight ofthe spun yarn, and wherein the sheath constitutes from about 10 wt. % toabout 50 wt. % of the spun yarn based on the total weight of the spunyarn.
 14. The composite material of claim 11, wherein the staple fibershave a length of from about 5 millimeters to about 75 millimeters.
 15. Amethod for forming a composite material, the method comprising applyingheat and pressure to a fabric to form a composite material, Page 3 of 5wherein the fabric comprises a yarn, wherein the yarn comprises a coreof continuous filaments of an inorganic material and a sheath of staplefibers of a thermoplastic polymer, further wherein the heat applied hasa temperature greater than the melting point of the thermoplasticpolymer and the pressure applied ranges from about 50 psi to about 2000psi.
 16. The method of claim 15, wherein the yarn is core spun, ringspun, air jet spun, friction spun, or vortex spun.
 17. The method ofclaim 15, wherein the continuous filaments are coated with a binder. 18.The method of claim 15, wherein the composite material is shaped into amolded article by placing the fabric into a mold before applying heatand pressure.
 19. The method of claim 15, wherein the inorganic materialcomprises fiberglass, carbon, ceramic, quartz, or a combination thereof,and wherein the staple fibers comprise polyetherimide, polycarbonate,polypropylene, polyethylene, polyphenylene sulfide, polyethyleneterephthalate, polybutylene terephthalate, polyethersulfone,polyetherketoneketone, polyetheretherketone, polyamide, or a combinationthereof.
 20. The method of claim 19, wherein the staple fibers comprisepolyetherimide and the heat applied has a temperature ranging from about200° C. to about 400° C., or wherein the staple fibers comprisepolycarbonate and the heat applied has a temperature ranging from about100° C. to about 275° C.